1. Field of the Invention
The present invention relates to a wide-angle projection zoom lens that is used as a projection lens of, for example, a projector, and more particularly, to a wide-angle projection zoom lens that is suitable to enlarge and project the original image formed by a light beam which is modulated by a light valve, such as a liquid crystal display element or a micromirror device, onto a screen and a projection display device including the same.
2. Description of the Related Art
In recent years, a so-called front projection projector that projects an image onto a screen that is provided in front of the projector has been widely used for school education, business training, or presentation. In addition, with the digitization of television broadcasting, there is an increasing demand for a system that can display an image on a large screen in the home. Therefore, there is an increasing demand for a front projection projector with a screen size of more than 80 inches.
A projection lens provided in the projector needs to have a small size and a wide angle of view in order to prevent light from being incident on the eye of an explainer or a presenter who stands near the screen or prevent a projection image from being shielded by the explainer or the presenter, and in order to increase the screen size in a small room space. In addition, there is a demand for a projection lens with a zoom function in order to facilitate the alignment of a screen size with a projection screen size.
In recent years, a transmissive or reflective liquid crystal display element or a digital micromirror device (DMD) manufactured by Texas Instruments Inc., which is a representative example of a micromirror device, has generally been used as a light modulating device (light valve). However, a projection lens used for a projector using the light valve needs to have a long back focal length and a telecentric reduction side (light valve side).
For example, JP-A-2007-225877, JP-A-2007-304268, and JP-A-2009-014819 disclose projection zoom lenses that meet the above-mentioned demands.
In recent years; there is an increasing demand for an apparatus that can project a clear image in a relatively bright room environment such that the user can read data or take a memo while viewing the image projected onto the screen.
It is preferable to obtain a fast projection lens with a small F number in order to meet the demand. It is difficult to effectively correct various aberrations while obtaining a wide-angle and fast zoom lens. In particular, it is difficult to prevent an increase in the various aberrations in the periphery of the screen.
JP-A-2007-225877, JP-A-2007-304268, and JP-A-2009-014819 do not disclose a zoom lens that can meet the above-mentioned demand and has a high speed of F1.6 and an angle of view of more than 70 degrees at the wide angle end.